Rotating equipment, such as the rotors of an electric motor, are inherently unbalanced due to variations in material and manufacturing tolerances. Unbalanced operation accordingly results in vibration. The magnitude of vibration is related to the magnitude of unbalance, and increases as the rotating speed approaches the rotor's natural frequency (the rotor's critical speed). It will be appreciated that for flexible shaft rotors, critical speed is less than operating speed. One of ordinary skill in the art will understand that vibration undermines the performance of rotating equipment such as an electric motor. Further, continued episodes of vibration will limit the life of the rotating equipment and will result in higher maintenance costs. Therefore, there is need to minimize vibration in rotating devices such as electric motors.
For example, as a flexible shaft rotor transcends its critical speed, which occurs within its operating speed, the magnitude of vibration increases. The magnitude of vibration can be reduced by providing balancing of a third balancing plane, which in a rotating device such as an electric motor is located in close proximity to the rotor's geometric center. By providing a third plane for balancing, the counter balance weight can be distributed such that the force due to unbalanced weight can be reduced to a negligible amount throughout the entire speed range of a rotating device.
Conventional systems and methods for balancing a third plane of a rotating device require the removal of active material, such as electrical steel laminations at the center plane location. This in turn requires a longer rotor core to compensate for removal of active material. It will be appreciated that another disadvantage of conventional systems and methods for minimizing vibration of rotating devices is that the rotor must be entirely removed from the rotating device, such as a motor, for each balancing attempt. Accordingly, there is an unmet need to effectively and efficiently minimize vibration of a rotating device by balancing a third plane.